Rubber sheet tensioning device for offset printing machines

ABSTRACT

A rubber-blanket clamping device for offset printing presses, which comprises a rubber-blanket cylinder and a rotatable and lockable clamping shaft which has a continuous longitudinal groove. The clamping shaft is disposed in a recess which has a longitudinal slot and extends parallel to the axis of the rubberblanket cylinder. The clamping shaft receives both ends of the rubber-blanket equipped with reinforcing strips. The latter are clamped in the longitudinal groove upon rotation and arresting the clamping shaft. The width of three of the metal strips gripping the ends of the rubber-blanket are equal with the depth of the groove, and a fourth front metal strip, viewed in the direction of rotation of the clamping shaft, is wider by the distance between the clamping shaft surfaces and the wall of a cylindrical bore defining the recess.

United States Patent 3,276,364 10/1966 Langer RUBBER SHEET TENSIONING DEVICE FOR OFFSET PRINTING MACHINES 2 Claims, 2 Drawing Figs.

U.S.Cl 101/4l5.l Int. Cl i B4lf 7/22 FieldoiSearch 101/415.1,

ReferencesCited UNITED STATES PATENTS 3,296,673 1/1967 Kirkpatrick 3,332,346 7/1967 Luehrs ABSTRACT: A rubber-blanket clamping device for offset printing presses, which comprises a rubber-blanket cylinder and a rotatable and lockable clamping shaft which has a continuous longitudinal groove. The clamping shaft is disposed in a recess which has a longitudinal slot and extends parallel to the axis of the rubber-blanket cylinder. The clamping shaft receives both ends of the rubber-blanket equipped with reinforcing strips. The latter are clamped in the longitudinal groove upon rotation and arresting the clamping shaft. The width of three of the metal strips gripping the ends of the rubber-blanket are equal with the depth of the groove, and a fourth front metal strip, viewed in the direction of rotation of the clamping shaft, is wider by the distance between the clamping shaft surfaces and the wall of a cylindrical bore defining the recess.

PATENTEU JUNI 5 Ian INVENTOR WOLFGANG SCHULZ ATTORNEY.

The present invention relates to a rubber-blanket clamping device for offset printing presses.

For the fastening of the rubber blanket to the rubber-blanket cylinder of offset printing presses, the most varied devices have become known. Common features of the known devices are, that the rubber-blanket cylinder is provided with a longitudinal slot which extends parallel to the axis of the cylinder and widens inwardly to form a recess. One or two clamping shafts for the fastening of the rubber blanket are mounted in the recesses.

The clamping shafts are provided with longitudinal grooves which extend over the width of the blanket. The ends of the blanket which are reinforced with metal strips, are inserted in these grooves. The metal strips also protrude beyond the width of the rubber-blanket, so that on both sides of the rubber-blanket the sliding out of the metal strips and thus of the ends of the blanket is avoided by rotatable closure pieces, by covering of the grooves. By turning the clamp shafts or one clamp shaft, the blanket is then tightened.

In these devices a high expense is necessary for the working of the rubber-blanket cylinder, since the entire segment of the rubber-blanket cylinder, in which the clamping device is disposed, must be made by itself generally in two parts and the two parts must then be individually fitted and screwed to the remaining cylinder.

In particular, for this reason, there are still preferred clamping devices with wide clamping channels. In this connection it has to be taken in stride that a wide strip is lost for the actual printing surface. However, there is the possibility of being able to introduce the ends of the rubber-blanket, which in this case are also reinforced by metal strips, into the slot, which are arranged in the clamping channel and are readily accessible. However, in this case, there is the disadvantage, that a large part of the rubber-blanket cylinder is not available for the printing, so that this solution does not enter into consideration for web offset printing presses.

In order to avoid this disadvantage, there have become known arrangements in connection with which only one clamping shaft is present in each rubber-blanket cylinder, the shaft receiving in a longitudinal groove both ends of the rubber blanket, which are provided with reinforcing strips. In this arrangement, the wall of the groove, which is towards the rear in the direction of rotation of the clamping shaft, is provided with a strip shaped elevation, behind which a part of the reinforcementin this case again a metal stripis placed. The same reinforcement is provided onthe opposite side of the blanket also again with a strip shaped elevation behind which the reinforcement of the second end of the blanket rests. By turning the clamping shaft, the reinforcement are clamped behind the corresponding strip shaped elevations and it is thereby possible to obtain a uniform tension. With these devices, however, the cost of manufacture, for instance of the groove in the clamping shaft through the strip shaped elevation, is relatively high. Furthermore, there is the possibility that the reinforcements, without this being noted, will not engage fully behind the strip shaped elevations upon insertion thereof, which can lead to a clamping outside the groove.

This is supported by the fact, the due to the narrow longitudinal slot it is not possible to observe visually the correct or defective seating of the reinforcements.

It is one object of the present invention to provide a rubber blanket clamping device which avoids the disadvantages of the known devices and to provide a simplification in manufacture and assurance that even upon inaccurate insertion of the ends of the rubber-blanket a dependable tightening is made possible.

It is another object of the present invention to provide a rubber-blanket clamping device which makes it possible for both ends of the blanket to be introduced readily into a recess which can be easily produced and by which the ends of the blanket are automatically forced into a groove of to clamping shaft and held fast there upon the tightening.

It is yet another object of the present invention, to provide a rubber-blanket clamping device wherein the width of three reinforcing or metal strips is equal to the depth of the longitudinal groove while a fourth metal strip which is located towards the front in the direction of rotation of the clamping 0 shaft is wider by a distance equal to the distance between the surface of the clamping shaft and the wall of a cylindrical bore which forms the recess. The longitudinal slot of the rubberblanket cylinder has on the front side as seen in the direction of rotation of the clamping shaft, an entrance slope which is tangent to the borehole and extends over the entire width of the cylinder, for the introduction of the wider metal strip. This metal strip can then be fixed in its position during the clamping process by means of the cylindrical bore.

With these and other objects in view, which will become apparent in the following detailed description, the present invention will be clearly understood in connection with the accompanying drawing, in which:

FIG. I is a schematic cross section through the rubber-blanket clamping device of a blanket cylinder in accordance with the present invention, just after the insertion of the blanket ends, and

FIG. 2 is a schematic cross section, similar to that shown in FIG. 1, but with the rubber-blanket clamped in position.

Referring now to the drawings in the blanket cylinder 1 there is provided a cylindrical bore 2 which has a longitudinal slot 3 extending towards the cylindrical surface of the rubberblanket cylinder 1. A clamping shaft 4 is guided in the bore 2, which is provided with a groove 5. Both ends of the rubberblanket 6 are reinforced by metal strips 7, 8, 9 and 10, the metal strip 10 being wider than the metal strips 7, 8 and 9. In this connection the wider metal strip 10 is arranged on the front side as seen in the direction of rotation of the clamping shaft 4. An entrance slope 11 which is tangent to the borehole 2 from the longitudinal slot 3 provides assurance, even when the metal strips 7, 8, 9 and 10 and thus the ends of the rubberblanket 2 have not been accurately inserted up to the bottom of the groove, that by the application of the resting surface 10 of the metal strip 10 against the entrance slope 11 during the clockwise rotation of the clamping shaft, the metal strip and thus the two ends of the rubber-blanket will be pushed all the way to the bottom of the groove. The rotation of the clamping shaft is effected, for instance by a worm gearing and does not constitute an object of the present invention. Due to the fact that the resting surface 10 of the metal strip it) rests against the wall of the cylindrical bore 2, the one blanket end located between the metal strips 9 and Ill is pressed firmly into the groove during the entire clamping process and at the latest as from the moment when the surface It) has left the entrance slope Ill, as well as in tensioned condition. Since this end of the blanket places itself even before the tension commences over the other end of the blanket, which is reinforced with the metal strips 7 and 8, the other end is also firmly in the groove.

In order to replace the rubber-blanket, the clamping shaft 4 is merely turned back into its initial position and the ends of the rubber-blanket can easily be removed via the longitudinal slot 3 out of the groove 5 and thus from the rubber-blanket cylinder 1..

While I have disclosed one embodiment of the present invention, it is to be understood, that this embodiment is given by example only and not in a limiting sense.

Iclaim:

1. A rubber-blanket clamping device for offset printing presses, comprising:

a rubber-blanket cylinder having a recess defined by a cylindrical bore extending axially of said cylinder,

said recess having a longitudinal slot extending to the surface of said cylinder, a rubber blanket with each end thereof being sandwiched between two metal reinforcing strips,

of said clamping shaft, being wider than the depth of said groove by the distance between the clamping shaft surfaces and the wall of said cylindrical bore defining said recess. 2. A rubber-blanket device, as set forth in claim 1, wherein said longitudinal slot has on the front side viewed in the direction of rotation of said clamping shaft an entrance slope, which is tangent to the bore and extends over the entire width of said cylinder, adapted for the introduction of said wider metal strip and lockable in its position by means of said cylindrical bore. 

1. A rubber-blanket clamping device for offset printing presses, comprising: a rubber-blanket cylinder having a recess defined by a cylindrical bore extending axially of said cylinder, said recess having a longitudinal slot extending to the surface of said cylinder, a rubber blanket with each end thereof being sandwiched between two metal reinforcing strips, a rotatable and lockable clamping shaft having a continuous longitudinal groove, said clamping shaft being disposed in said recess and extending parallel to the axis of said blanket cylinder, said clamping shaft receiving both ends of said rubber blanket equipped with said reinforcing strips, the latter being clamped in said longitudinal groove upon the rotation and arresting of said clamping shaft, the width of three of said metal strips gripping the ends of said rubber-blanket being equal with the depth of said groove, and a fourth front metal strip, viewed in the direction of rotation of said clamping shaft, being wider than the depth of said groove by the distance between the clamping shaft surfaces and the wall of said cylindrical bore defining said recess.
 2. A rubber-blanket device, as set forth in claim 1, wherein said longitudinal slot has on the front side viewed in the direction of rotation of said clamping shaft an entrance slope, which is tangent to the bore and extends over the entire width of said cylinder, adapted for the introduction of said wider metal strip and lockable in its position by means of said cylindrical bore. 